Lighting systems that utilize light guides are known in the art. In such lighting systems, it is important to reduce the leakage of light from certain surfaces of the light guide as much as possible. By reducing such leakage, the optical efficiency of the system may be maximized. In addition, it is possible to avoid a brighter edge pattern around the light guide. Avoiding a brighter edge pattern is particularly important for light guide panel tiling illumination system.
FIG. 1 illustrates a conventional light guide-based lighting system. Light from a source 10 is coupled into a light guide 12 via an incident edge surface 14. The light from the light source 10 travels within the light guide 12 and is subsequently extracted out by extraction features 16 formed on a bottom surface 18 of the light guide 12. The extracted light 20 is emitted through a top surface 22 of the light guide 12. In such a conventional lighting system, however, even though the extraction features 16 may be well designed and manufactured there may still be light leakage taking place. As is shown in FIG. 1, light leakage 24 will still occur at an edge surface 26 of the light guide 12 and thereby continue to reduce optical efficiency and brightness uniformity.
Previous efforts to reduce light leakage in a light guide involve including structures on the surfaces of the light guide. For example, US 2007/0086208 A1 (Seoung Ho Lee et al.) describes a microstructure on the light guide to prevent light loss on an incident surface facing the light source unit. US 2005/0105282 A1 (Tai-Cherng Yu et al.) describes a surface light source comprising a light guide plate with a large number of prisms at the emitting surface, in which a distance separating two adjacent prisms changes according to an intensity of the light beams received from the light source.
While such previous efforts may be suitable for many applications of lighting systems, there remains a strong need in the art for further reduction in light leakage within a light guide. In particular, there remains a strong need for a light guide which further maximizes optical efficiency and reduces formation of brighter edge patterns.